lotus notes 8.5 fixup

so I'm new to lotus notes, and this question is probably over kill since i am just a user, and don't administer the server, but in another questions it was suggested to try running fixup. so i started googleing fixup and found this statement "Keep in mind that after you set up transaction logging, Fixup is not needed or used to bring databases back to a consistent state." so I can't help but wonder why you wouldn't need something to fix a corrupted database if transaction logging is set? this suggests that transaction logging keeps databases from becoming corrupt. is that what transaction logging does? if so how?